Gritty mix no good for pawpaw seedlings
In the spring of 2010 I germinated several paw paw seeds (Asimina triloba). I planted them in clear 3 liter soda bottles, some in the gritty mix, and others in 5-1-1- mix. By the end of the year, the ones in the 5-1-1 mix had grown quite a bit more on average. In 2011, I repotted some of the gritty mix plants in 5-1-1 mix, and they did much better than those that I left in the gritty mix. I left a few in the gritty mix until this week. They looked even worse in 2012 and this year.
Notably, I could never see any roots through the side of the container, though I did see tap roots reaching the bottom. In the 5-1-1 mix, I could see roots at the side of the container by the end of the first season.
I repotted the remaining few this week, and the lateral roots were really sparse. I don't know if it's because few lateral roots ever formed, or if some of them died back. Several of the remaining lateral roots were dead. I planted 2 in 5-1-1 mix, and tossed one that was barely hanging on.
I've had success growing other plants in the gritty mix, including elm and silk tree, as well as several different house plants, so I think I'm making it correctly.
So, I'm not sure why the paw paw roots were so unhappy. Pawpaws are in the magnolid group of dicots, and have thick fleshy roots, with no discernible root hairs. Among fruit growers, pawpaws have a reputation of having some unusual requirements/preferences because of the behavior of the roots.
With that in mind, I'm wondering if anyone else has had poor results growing magnolids (magnolias, avocado, sassafras eg) in the gritty mix?